Electric measuring apparatus



p 9 3 H. P. KUEHNI 2,329,541

ELECTRIC MEASURING APPARATUS Filed June 18, 1941 2 Sheets-Sheet 2 Fig. 6.

, 74 7a 72 ea 3 [gm Fig.7

Inventor:

I v Y 70 Q I lllllllllllllllllllllfllfllllllllllllll1% Hans P. Kuehnif Patented Sept. I4, 1943 2,329,5 4 1 v g V {anaemic MEASURING APPARATUS Hans R Kuehni; (Schenectady; N. Y., assignorto I 1 .General Elcctric lompany, a corporation of j 4 l Newyork; v

it Applies tailbone 1 s, 1941; Serial N5. 398,579

' ,g 'slolaims. ,(o1 265 1) Myinventionrelates-*to -an electric-measuring apparatus, and although'notf-limited theretodt has -application to a machine tool force measuringgage'of the electromagnetic type."

objectof my invention is to providean improved measuring apparatus of the-above mentioned-type which simple iirconstruction, reliable in operation; and easy to manufacture;

* Ano tlrior"ob frec t or my invention is toprovide an electric measuring' device having an improved gage head for measuring the components offorce applied-to a member, along a plurality-- of'axes.

A further object of my invention is to provide an improved-machine tool force measuring "gage and-cutting prssureof atool bit. Further 7 objects and advantages-of my; invention will become apparent fromthe'followingdefor simultaneously masuring the feed pressure s scription r'ef-erring to the accompanying drawings,

' andtheieatures of-novelty which characterize my intention will be pointed out -with particularity 'inthe claims-- annexed to and forming a. part -'of this-specification;

1 ln the drawings Fig; lis aperspective' ie'w-fof 'a-nrachinetool'force measuring gage holding a 'toolbit which is cutting a shaving; from a Work piece, the (gage; being provided with "an'embodi- -"ment of my invention; Fig. 2 isa" sectional side elevation of; the gage {head illustrated in Fig; 1

Figs? is"an-- end -view in' partial section, illustratingone ofthe gage coils and cooperating ar- 'mature-o'f' the gage-head illustratedjin'Fig. 2'; Figs. 4 and 5 *ill-ustratediagrammatically electrical circuits for obtaining electrical indications M proportional to the feed pressureand cutting pre'ssu'reofthe bit carried by my improved m a-, -chine tiool force measuring gage; Fig. 6 illustrates a; modific'ationof the machine tool force measuring device illustrated'in Fig's. 1, 2, and 3,

"and Fig, 7 illustratesdiagrammatically an electrical circuit for obtaining-indications proportionalnto components of force acting-on the tool 7 1 In thearrangementillustrated :in the drawings, H

l ghaveprouid'darnachine toolforce measuring or pressure gage with a gage head having a plurality-otJgage'=coi-1s supported by-a body portion onlzmutuallly' perpendicular axes ina plane, and -a member having let/plurality of :armatures 'adja- W p, c ntrthe gage co'ilsuand cooperable: magnetically -50 its-herewith. The body portion: and :member 'are'in :the 'fox'm otltwo:'concentricimembers, the tool =bit along an axis atrdz tipon "rotation ofr thelwork fifi piece, relative movement will be causedbetween the armatures-and' the coils due to contact be tween the bit and 'w'ork piece, which will vary the reactance of thecoils. This Variation in reactan'ce will'produce a change in the cur-rent passing through the gage coilspz oportionalto the amount bf relative-movement betweenthe c(')ncent ric'- members'along the-axes I In the ap+ plicationof my invention tea-machine tool force measuring gage; the gage deviceswiththe coils are disposed along mutuallyperpendicularaxes, that-is, along an-axispara-lle1 with'the -airis of bodilymo'vement of the gage head along the work piece-for measuring-feed pressure, and along an a ris -perpendicularthreto for measuring cuttingpressure; It-isto be understood, however, that the magnetic members and gage-coils may :be placed along any suitahla number of axes have-fanysuiltable relationship to each other, for measuring the components of the force along these axes,- and it is also tobe understood that my invention has-application to any-measurin'gdevice in which it is desired tomeasure one or all of the com-ponents of a force which is actihgupon a member. With these coils suitably :connecteddnbridge circuits; the change in -rea-ctan 'ce of one of the "coils willgive an indication of th e'movement along that axis, While the change in. reacta'nce of the other coil willgivef'an indication of? the relative movement betweenfthe tubular members along anotheryaxis. Such displacement indications maybe calibrated, if desired, into feed pressure and, cutting pressurev of the toolybit on thework piece; a v

Referring to Figs; 1" to'3,.I have illustrated a measuring appara'tusmounted "as a 'machineltbol force measuring gage for measuring the feed pressure and'cu'ttihg pressureof a tool bit; I G as it axiallyn oves alongthe surface-of. a rotating work piece it in. order to cut a predetermined amount from the, -workpiece MI in a predetersmined time which. is indicated by the si ze of the shaving I2. The measuring apparatus includes engage head indicated generallylby; the-numeral {-3 and a supporting member I4-which isheld by .aflat plate l5 :in'any suitable manner. ;;'Iheplate I5 is provided with an open groove portion 16 which inturnis adapted to cooperate. with a :tongue portion l1. This tongue portion is bolted ,to the gage supporting member M by a plurality ;of bolts'l8.andgcooperating nuts 19. Any suitable-ynower means maybe provided for moving :thasumiorting member H: and plate lfiz'along an ."axisparallel with the axisof rotation. of/the work piece H, such as through a movable carriage or along any other suitable axis.

In order to provide an arrangement for giving an indication of the amount of displacement of the tool bit or the force acting thereon along any suitable number of axes, such as the horizontal and vertical axes, the gage head I3 is provided with a body portion or supporting tube 20 and a member or tube 2|. As will be seen in Fig. 2 the body portion 23 and member 2| form two conportion 22 is provided in one of the faces of the supporting members :4, in order-to receive an end of the body member 2 which is tightly held in position by a plurality of bolts 23-which extend through bores 24 in the supporting member and thread into cooperating bores 25 in, the

- body portion. Enlarged holes 26 connect with the bolts in order to provide a suitable aperture through which a tool may be placed for tightening the bolts 23 or loosening them when it is desired to remove the body portion from the supporting member. The tube 2| or rod may be supported in spaced relationship with the body portion 20 in any suitable manner, and in the arrangement illustrated in the drawings a portion of the tube extends into a cooperating bore 2'1 in the supportingmember. The tube may be tightly held in the bore 21 in any suitable manner such as by providing a shrink fit between the tube and the surrounding surface of the supporting member which defines the bore 2'1. In order to provide an arrangementior conveniently holding the tool bit It] by the gage head I provide abore 28 in the tube 2|. The tool bit may, therefore, be inserted in this bore 28 and tightly secured therein by a screw 29 which is provided in a threaded hole 30 in the tube 2|. A cap 3| screws into a hole in the body 20 in registry with the hole 33 so as toprovide a closure for the hole 30 which may accommodate a tool to tighten or loosen the screw 23. A cover 3-|' is also placed over the end of the body 23 and a portion of the tube 2|, and this cover together with the cap 3| prevents any coolants which are played on the tool bit from entering the space between the body 20 and the tube 2|. Furthermore, since heat from the tool bit may be transferred to the member 2|, it may be made of any suitable material which has a minimum thermal coefl'icient of expansion, so as to minimize any inaccuracies in the gage. Also the gage may be calibrated to take into account any predetermined expansion of the parts. When the tool bit is held by the gage head and is then forced against the rotating work piece, as illustrated in Fig. 1, the gage being moved along an axis parallel with the axis of rotation of the work, the tool bit will be acted upon by a force, and since the member 2| is relatively flexible, the cantilever portion extending from the supporting member l4 will be moved a small amount in some direction. Thisforce and movement may be resolved into components along suitable axes, such as along mutually perpendicular axes, which may be horizontal and vertical axes. In order to provide 'an'arrangement for indicating the components of this force any suitable arrangement may be employed, and in the illustrated embodiment of my invention I provide a plurality of coil members 32 and 33, the coils 32 being on one axis, or a horizontal axis as seen in Fig. 3, and the coils 33 being on a vertical axis. These gage coils 32 and 33 may be of the conventional type and each includes a pair of coils 32, being wound around a cooperating core member 34, and the coils 33 being wound around a core member 35. Any suitable arrangement may be provided for changing the reactance of the coils in proportion to the force or displacement which is to be measured. Therefore, I provide a plurality of armatures 36 and 3'! which are supported by the tube 2| in any suitable manner, such as by a plurality of bolts 38, so

that the coils 32 and 33 may cooperate electrocentric tubular members each of which is supported by the supporting member l4. A recessed magnetically with the armatures 35'and 31. Instead of employing separate armatures the member 2| may be made of suitable magnetic material if desired. The armature 35 is mounted adjacent the gagecoils 32 and the armature 31 is mounted adjacent thegage coils 33 sothat movement of the tube relative to the body portion will move the, armatures relative to the cooperating gage coils in order to vary the air gap therebetween and change the reactance of the coils. Thus,

the change in air gap between the armature 35 and the cooperating gage coils'32 will give an indication of the component of force acting on the tool in a horizontal direction, and the change in the air gap between the armature 3'! and its cooperating gage coils 33 will give an indication of the component of force acting on the toolin a vertical direction. The gage coi1s 32 and 33 may be supported on the body portion in any suitable manner, such as by plates 39 and 40, respectively,

which are in turn held tightly against the outside surface of the body portion by a plurality of screws.

In order to provide an arrangement for indicating simultaneously these components of force acting on the tool bit, the gage coils 32 and 33 may be connected in any suitable circuits. Thus, as illustrated in Fig. 4 the gage coils 32 inseries and here represented as a single winding maybe 40 connected in one arm of. abridge circuit through conductors 42. These conductors are accommodated in the bore 28 and a' suitableconnector 43 may be provided at the end of the bore in order to hold tightly the conductors therein so that no strain will result at the connection between the conductors and the gage coils. A balancing unit 44 is provided in another arm of the bridge and a reactor having portions 45 and 46 is provided for the other two arms of the bridge.

The bridge is energized from a suitable source of power indicated at 41 which is connected at conjugate points of the bridge. The other conjugate points 48 and 49 are connected through a suitablerectifier arrangement indicated by the numeral 50 to a suitable indicating arrangement such as a galvanometer 5| As will be seen in Fig. 5 the gage coils-33 here represented as a single windingare connected in a circuit similar to that indicated in Fig. 4 so that a meter 5| may give an indication of the amount oi displacement of the armature 31.

Thus,,withthe tool bit being out of engagement with the work H, the tube 2| will be stationary with respect to the body portion and 5 'air gaps of predetermined amountswvill exist between the armatures and the cooperating cores of the gage coils. Through the arrangement of the balancing units, the bridgecircuits shown in Figs. 4 and 5 may be balanced 'sothat the meters 5| and 5| will'indicate that there is a normal air gap at the gage coils or that predet'ermined conditions exist for the tool .bit. However, upon moving the tool bit into engagement with the .work and starting the-machine tool'tooperate so that the work will rotate about an axis as curiedto the body por vder 6'! and a'lock nutBB, and thebar 53 istightlyceo able. manner, such as by indicated by the arrow andthe gage h'ead and toolbit 'will move in a direction: parallel with theaxisrof. rotation of the work.in order that the. bit will'cut a shaving indicated by the :nu-

meral l2, the tool bit will 'be acteduponby a a force which will in turn move the member 2'! with respect to the body portioni20; the elastic ch'aracteristics-of the member-2| being determined by the force which it: must..absorb sothat' the =-:de sirable. displacement Y will be' obtained. As 1 a result. of. this force, the. movementv of: the tool: bit may be resolved intooomponents along.- axes perpendicular to each other and one .comp'onen't'wi ll be; indicated by :the change in air.- ;gap.;b'etween thep-coils 325V and armature 3B5 whileitha-otlier component along the other..axis willbe indicated by. the ;'change in air; gap. betweenz thergage iCOflS 33- zand their cooperating armature 3.3.; These componentsralong these two) axes .Willi'b' indicated. separately and. simultaneously; byyrthe meters or suitable indicators 5l..and 5l.'.. .These indicators may, therefore, becalibrated to; indicate displacement in somefunit of-di'stance,=or by. determining theamount of force necessary to;move the bit a unit of. distance the meters 511 and 51? may be used to indicate" thehorizontal and vertical. components off the force actingflupon the tool bit. Thus, the meteril may be made to indicate the feed pressure while the meter 5.1 may be used to indicate the-cuttina pressure of thetool bit. .c

In. Eig. 6 I have illustrated a modification of my electric measuring apparatus; illustratedv in Figs. 1; 2, and 3 which-has applicationtoia'machine tool force-,rneasuring gageandwhich includes the gage head indicated generally by the numeral-.60 and a supporting member; Blwhich is heldin any suitable manner suchas bya flat plate l5 in a manner similar to the way in. which the supporting member M is held'by theflat plate in -Fig. 1. Here again any suitable power means maybe provided for moving thesupporting member ti and plate l5 along any suitable axis, such as an axis parallel with the axis of cooperate with the tool bit It; flhe..-gage head includes a body portion 62 and abar member-6,3 .whichis adapted .to support the tool .bit in a hole I as, the bit being tightly held in the hole; by. a cooperating screw 65. The rod 63 may be-supportedbythe body portion 62 many suitable manner. ;ar1.d in g the arrangement illustrated in the drawings the membersare concentrically arranged, thebar;beingsupported.near one end of the; body portionfiZ; through a diaphragm 66 which has suificient flexibility to allow movement of the bar 83 a suitable amount in the; desired lateral directions. The diaphragm-is tightly. .setion-GZ b etween' a shoulheldin the bore of the diaphragm in anysuitwelding which is' indicated by the numeral 69. A plurality of pins, 161 may extend from holesin thebodyfiZ into, holes in the diaphragm att in; order toaabsorb ,an'y torque. Any other suitable arrangement maysbe provided for mounting the rod member for limited :relative movement with respect tothelbody mem- In order to provide anarrangementufor 'iorce onthe barmemberqfli' f'lthe supporting member 66 her-62.

providing a reactive on the opposite side 0 than the bit;v which. reactive force willxbeizproportionalto the iorceactingco'n the bit,'I provide a :suitable rod or resilient member 1.9; which is relativelytightly heldl in 'a :bore l I ottheibody suitablel arcuate; shaped bore 114 through which extendszthe resilient rodmember 70. '-A suf-- ficient clearance is provided'b'etweenthe resilient member-3T0 and the smallest portion. of thebore M sothatthe. rod may be received thereby when the rod' member'fiiiiis inserted in 'theubodyi portion62.

In order to measure. the componentcf 'the force acting onxthe toolbit ill in adirection per.- pendicular to the direction of bodily. movement ofythe gage. device, which will be a vertical. directioh'if: thegage device is mounted iormovementr'in the horizontal direction, I provide a gage coil 15 whichismounted on the body'portion- B2 throughabolt 16 andnut 11. The. boltv'ltcma'y be made of suitable magnetic material so that it will provide aicore member-for the coili15;: Also by making thebolt members of suitable'dimensions rand byrrotating the-:nut H the air gap berotation of the Work piece which is, adaptedto $.45

tween-the; resilient r member '10 "and: the cooperating end of the bolt 16 may be adjusted; A zgag'escoil. 18 similar tosthe-coil 15 may./be 'placed on. a.diametrically opposite side of the resilient-- rmembenlill sul ortedibyz a'bolt .19i'and a; nut tfliso that whe'nthe air. gapbetwe'en' the resilient member 10.: andithe 0011311163118 aincreasedfthew'giapbetween the core. .19. :and the resilient wmemberll 0 willbe: decreased; 1 fT-hese gage coils may be suitably conn'ecteddn 'ai'circuitias illustrated in Fi-g; '7 so as topn'reasure the change-inrreactance :off the coils .due to; the change 'in .air gap. "Thus the coils 1.1.5.." and 1: 51:8 tare iser'ia'lly connected together in circuit with a reactor 81 :to form the fourar ns act a bridge. :circuit. A; suitable sourcie wof alternatin g. current isxconnected between the cuils: 1 5

and I8 andythe.;midepointiof the reactor-fill: and

the; oppositeuco-njiigate. points: of the bridge 'circuitgareiconnectedthrough a suit'able rectifier in- :dicated by; the numeral. 82 r to at suitable: meter ;z83i-whijch;imay-bet= calibratedito? read ineunits of {forces In; order-5th .measure zthe. component. of .force along "an axis -para'llel withgtheiiaicisli din-movement of thezgagezlieadififl,.aigage coilfl'ilis placed 'alongczsuch. :an axis which; is .similar.-to the gage :coils J Sand '18: andrwhich has a rcorezmember. for :coioperating with: the; relatively resilient member 1.0.. A tsimilarsigage .coil is providednonz 1a ."diametrically opposite side otIathe resilient member 10,. its: supporting. bolt and core I mernlec-ir beiug shown atz85, these"two:lattergagei coilsbeing connected iineaactrcuit similar to that -'illustrated in Figs 7; .for measuring the tool feed 'pressure.

order to provide. an arrangement:foreooperating .--niagnetically with .the omes; t11e=rod 5 m may be made oh -suitable magnetic material, "or the portion thereof adj acezi the-cores, or -arm'atures siniilaz to'ifl'fi and may lee-suitably carried by the rodJOL 7 @It: wilkbe seen measuting age asillustrated-in Figifijthe side act the body: portion 52 is effectively-sealed from .sandlthe range of operation-of the electric measuringw de-vice may be varied by mer'ely-qvarying the "amount otlreactive forceneeessary'to be bed through t im-relative resinentvmefirbeein; rims,

iat wi th th'e tool pressure force the force. acting on the tool bit times the distance. between the point where the'force: is applied and the, diaphragm 66 will be'equal to the distance between that diaphragm andlthe point of contact .between the nut "I4 and the bar 19 times the force which must be applied through the bar so as to prevent continued movement of the rod 63 around the supporting member. 66. It will be seen that by removing .thelock nut 58 and removing the rod 63 access'may be, had to the nut 13 and it may be moved toany suitable position within the bore 12 so as to control the moment arm of the reactive force acting through the resilient rod 19. In this manner the force range of my improved electric measuring device may be adjusted. It will beapparent that the rod 'Hlmay have suitable elastic characteristics In view of the foregoing, it willbe seen that I have provided an improved electric measuring device for simultaneously indicating the various components of a force. acting on a member-along any suitable number of axes. Thus, my improved electric measuring device may be employed as a machine tool force measuring or pressure gage for indicating separately and simultaneously the feed pressure and cutting pressure of the tool bit. It is to be understood, however, that my improved gage construction may be employedwith any other suitable type of measuring apparatus for giving a continuous indication of the various components along suitable axes of a force applied to a body.

Although I have shown and: described particular embodiments of my invention, I do not desire to be limited to the particular embodiments described; and I intend inthe appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by letters Patent of the United States is:

1. Apparatus for obtaining'measurements indicative of the feed and cutting pressures to which alathe tool is subjected during cutting.

in a rotating work piece, comprising a supporting structure adapted to be carried on a lathe carriage so as to have theusual .feed and. cutting movements relative to a work piece, a stifiiy resilient rod rigidly supported at one end in said supporting structure, a lathe cutting tool. movably carried in said supporting structure in cutting relation to the work and in force transmitting relationto said rodso as to oausesaid rod to be bent in one direction in proportion to the.

feed pressure on said tool and in a direction per.- pendicular to the first mentioned direction in proportion to the cutting pressure on;said.tool, a pair ofvariable reactance devices having. stationary parts carried by said structure adjacent to said rod and having magnetic armature means-carried by and moved by the bending of said rod in said two directions to vary one reactance by one direction of bending andthe other reactance by the other direction of;bending and a pair of reactance responsive circuits in which said variable reactances are respectively connected for obtaining measurement of the bending, of said rod in terms indicative of the feed and cutting pressures to which said cutting tool is subjected.

2. In an electric measuring device, a tubular body portion, a bar member having a bore extending through a portion thereof, means for mounting said bar member within said body portion for relative lateral movement, a resilient member carried by said body member and extending into said bore, means for operatively connecting a portion of said resilient member within said bore to said bar member, relative movement between said bar member and said body portion causing relative movement between said resilient member and said body portion, and electromagnetic means for measuring the amount of said last-mentioned movement.

3. In an electric measuring device, a tubular bodyportion, a plurality of gage coils supported by said body portion, a bar member having a longitudinally extending bore, means for mounting said barmember within said body portion for .limited lateral movement, .a resilient member carried by said body member and extending into said bore, means for operatively connecting a portion of said resilient member within said bore to said bar member, relative movement of said bar member and said body portion causing relative movement between said resilient member and said body member, and means including said gagecoils for measuring the amount of said last-mentioned movement. r 4. In an electric measuring device, a tubular body portion, a plurality of gage coils supported by said body portion on mutually perpendicular axes, a bar member adapted to be acted upon by a force, said bar member having a bore extending through a portion thereof, means for mounting said bar member within said body portion for limited lateral movement, a resilient member carried by said body portion and having a portion extending into said bore and a portion of magnetic material adapted to cooperate with said coils, and a nut having threaded engagement with the surface of said bore and having a hole therethrough, said resilient member extending through said hole in said nut for operatively connecting said bar to said resilient member, action of the force on said bar member causing relative movement between said magnetic portion and said gage coils.

5. In an electric measuring device, a tubular body portion, a bar member having a bore extending through a portion thereof, means for mounting said bar member within said body portion for relative lateral movement, a resilient member carried by said body member and extending into said bore, means for operatively connecting a portion of said resilient member within said bore to said bar member, relative movement between said bar member and said body portion causing relative movement between said resilient member and said body portion, and electromagnetic means for measuring the amount of said last-mentioned movement, said operatively connecting means being adjustable so as to vary the range of said measuring device. 6. In an electric gage, an elongated hollow tubular member adapted to be secured at one .endin fixed relation to a tool carriage, a cutting tool extending from the other end of said member in work-cutting relation, tool holding means and gage coils supported within said tubular member on radial axes at right angles to each other adjacent to but out of contact with said tool holder, and magnetic armature means car- 7 ried by said tool/holder adjacent said coils for varying the reactance of the gage'coils in ac,- cordance with the movement of said tool holder.

HANS P. KUEI-INI 

